M120 Router Major Hardware Components
Table 1 lists the major M120 router components and characteristics.
Table 1: M120 Router Major Hardware Components
Component | Quantity | Function | Redundant | Field- | Offline Button |
|---|---|---|---|---|---|
FEB | 1–6 | Provides route lookup and forwarding functions from FPCs and CFPCs | Yes | Yes | Yes |
Cooling system | 2 front fan trays, 2 rear fan trays (4 fans) Front air filter | Cools router components | Yes | Hot-removable, hot-insertable | – |
Craft interface | 1 | Displays status and allows you to perform control functions | – | Hot-removable, hot-insertable | – |
FPCs | 1–4 | Connect PICs to other components and houses shared memory | – | Hot-removable, | Yes |
CFPC | 1–2 | Combination of a PIC and an FPC; contains the interface circuitry and the FPC as a single assembly | Hot-removable, | ||
PICs | 1–4 per FPC | Provide interfaces to various network media; receive incoming packets from the network and transmit outgoing packets to the network, performing framing and line-speed signaling for their media type; encapsulate outgoing packets received by the FPCs before transmitting them | – | Hot-removable, | Yes |
Power supply | 2 AC or 2 DC | Distributes needed voltages to components | Yes | Hot-removable, | – |
Routing Engine | 1–2 | Runs Junos OS ; maintains the routing tables, manages the routing protocols used on the router, controls the router’s interfaces, controls some chassis components, and provides the interface for system management and user access to the router | Yes | Hot-pluggable | – |
Field-replaceable units (FRUs) are router components that can be replaced at the customer site. Replacing FRUs requires minimal router downtime. There are three types of FRUs:
- Hot-removable and hot-insertable—You can remove and replace the component without powering down the router or interrupting the routing functions.
- Hot-pluggable—You can remove the component without powering down the router, but routing functions are interrupted until the replacement is installed.
- Requires router shutdown—You must power down the router before removing the component.
